Issue with Whirling Invader NPC

Hello,
Every few days in Silithus Whirling Invader mobs spawn. These mobs are broken. When a Whirling Invader dies, it does not drop loot and despawns immediately. Please look into this issue. Thank you.
Every few days in Silithus Whirling Invader mobs spawn. These mobs are broken. When a Whirling Invader dies, it does not drop loot and despawns immediately. Please look into this issue. Thank you.